My installation has the exhaust running forward like yours will.  I have a
1.8L GTI engine installed at 54 degrees with a diesel bellhousing.  I
modified the exhaust manifold to face forward, ran the exhaust straight
forward past the major frame member where the first muffler is then it
makes a 180 turn to the right side of the van goes back towards the
transmission mount takes a slight bend 45 degrees towards the right wheel
well then turns back straight towards the rear where another muffler is
installed in the space next to the engine.  I have hangers at the big bend
up front at the first 45 degree bend and at the rear muffler.  I have had
no problems with this system, other then the quallity of the first mufflers
which I put on.  Now with good mufflers (dynomax) the system is pretty
quiet, no harmonic problems, and haven't had any cracking in 15K miles.
You can build the entire system without any special equipment only straight
pipes and stock 90 and 45 bends.  I would rather have an unmodified outlet
manifold and I'm wondering if the Audi manifold would fit my engine?

Hope this helps,
Dave K.